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 /*

  * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/shared/parGCAllocBuffer.hpp"

 #include "memory/sharedHeap.hpp"

 #include "oops/arrayOop.hpp"

 #include "oops/oop.inline.hpp"

 ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) :

   _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL),

   _end(NULL), _hard_end(NULL),

   _retained(false), _retained_filler(),

   _allocated(0), _wasted(0)

 {

   assert (min_size() > AlignmentReserve, "Inconsistency!");

   // arrayOopDesc::header_size depends on command line initialization.

   FillerHeaderSize = align_object_size(arrayOopDesc::header_size(T_INT));

   AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0;

 }

 size_t ParGCAllocBuffer::FillerHeaderSize;

 // If the minimum object size is greater than MinObjAlignment, we can

 // end up with a shard at the end of the buffer that's smaller than

 // the smallest object.  We can't allow that because the buffer must

 // look like it's full of objects when we retire it, so we make

 // sure we have enough space for a filler int array object.

 size_t ParGCAllocBuffer::AlignmentReserve;

 void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) {

   assert(!retain || end_of_gc, "Can only retain at GC end.");

   if (_retained) {

     // If the buffer had been retained shorten the previous filler object.

     assert(_retained_filler.end() <= _top, "INVARIANT");

     CollectedHeap::fill_with_object(_retained_filler);

     // Wasted space book-keeping, otherwise (normally) done in invalidate()

     _wasted += _retained_filler.word_size();

     _retained = false;

   }

   assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained.");

   if (_top < _hard_end) {

     CollectedHeap::fill_with_object(_top, _hard_end);

     if (!retain) {

       invalidate();

     } else {

       // Is there wasted space we'd like to retain for the next GC?

       if (pointer_delta(_end, _top) > FillerHeaderSize) {

         _retained = true;

         _retained_filler = MemRegion(_top, FillerHeaderSize);

         _top = _top + FillerHeaderSize;

       } else {

         invalidate();

       }

     }

   }

 }

 void ParGCAllocBuffer::flush_stats(PLABStats* stats) {

   assert(ResizePLAB, "Wasted work");

   stats->add_allocated(_allocated);

   stats->add_wasted(_wasted);

   stats->add_unused(pointer_delta(_end, _top));

 }

 // Compute desired plab size and latch result for later

 // use. This should be called once at the end of parallel

 // scavenge; it clears the sensor accumulators.

 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) {

   assert(ResizePLAB, "Not set");

   assert(is_object_aligned(max_size()) && min_size() <= max_size(),

          "PLAB clipping computation may be incorrect");

   if (_allocated == 0) {

     assert(_unused == 0,

            err_msg("Inconsistency in PLAB stats: "

                    "_allocated: "SIZE_FORMAT", "

                    "_wasted: "SIZE_FORMAT", "

                    "_unused: "SIZE_FORMAT", "

                    "_used  : "SIZE_FORMAT,

                    _allocated, _wasted, _unused, _used));

     _allocated = 1;

   }

   double wasted_frac    = (double)_unused/(double)_allocated;

   size_t target_refills = (size_t)((wasted_frac*TargetSurvivorRatio)/

                                    TargetPLABWastePct);

   if (target_refills == 0) {

     target_refills = 1;

   }

   _used = _allocated - _wasted - _unused;

   size_t plab_sz = _used/(target_refills*no_of_gc_workers);

   if (PrintPLAB) gclog_or_tty->print(" (plab_sz = %d ", plab_sz);

   // Take historical weighted average

   _filter.sample(plab_sz);

   // Clip from above and below, and align to object boundary

   plab_sz = MAX2(min_size(), (size_t)_filter.average());

   plab_sz = MIN2(max_size(), plab_sz);

   plab_sz = align_object_size(plab_sz);

   // Latch the result

   if (PrintPLAB) gclog_or_tty->print(" desired_plab_sz = %d) ", plab_sz);

   _desired_plab_sz = plab_sz;

   // Now clear the accumulators for next round:

   // note this needs to be fixed in the case where we

   // are retaining across scavenges. FIX ME !!! XXX

   _allocated = 0;

   _wasted    = 0;

   _unused    = 0;

 }

 #ifndef PRODUCT

 void ParGCAllocBuffer::print() {

   gclog_or_tty->print("parGCAllocBuffer: _bottom: %p  _top: %p  _end: %p  _hard_end: %p"

              "_retained: %c _retained_filler: [%p,%p)\n",

              _bottom, _top, _end, _hard_end,

              "FT"[_retained], _retained_filler.start(), _retained_filler.end());

 }

 #endif // !PRODUCT

 const size_t ParGCAllocBufferWithBOT::ChunkSizeInWords =

 MIN2(CardTableModRefBS::par_chunk_heapword_alignment(),

      ((size_t)Generation::GenGrain)/HeapWordSize);

 const size_t ParGCAllocBufferWithBOT::ChunkSizeInBytes =

 MIN2(CardTableModRefBS::par_chunk_heapword_alignment() * HeapWordSize,

      (size_t)Generation::GenGrain);

 ParGCAllocBufferWithBOT::ParGCAllocBufferWithBOT(size_t word_sz,

                                                  BlockOffsetSharedArray* bsa) :

   ParGCAllocBuffer(word_sz),

   _bsa(bsa),

   _bt(bsa, MemRegion(_bottom, _hard_end)),

   _true_end(_hard_end)

 {}

 // The buffer comes with its own BOT, with a shared (obviously) underlying

 // BlockOffsetSharedArray. We manipulate this BOT in the normal way

 // as we would for any contiguous space. However, on accasion we

 // need to do some buffer surgery at the extremities before we

 // start using the body of the buffer for allocations. Such surgery

 // (as explained elsewhere) is to prevent allocation on a card that

 // is in the process of being walked concurrently by another GC thread.

 // When such surgery happens at a point that is far removed (to the

 // right of the current allocation point, top), we use the "contig"

 // parameter below to directly manipulate the shared array without

 // modifying the _next_threshold state in the BOT.

 void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr,

                                                      bool contig) {

   CollectedHeap::fill_with_object(mr);

   if (contig) {

     _bt.alloc_block(mr.start(), mr.end());

   } else {

     _bt.BlockOffsetArray::alloc_block(mr.start(), mr.end());

   }

 }

 HeapWord* ParGCAllocBufferWithBOT::allocate_slow(size_t word_sz) {

   HeapWord* res = NULL;

   if (_true_end > _hard_end) {

     assert((HeapWord*)align_size_down(intptr_t(_hard_end),

                                       ChunkSizeInBytes) == _hard_end,

            "or else _true_end should be equal to _hard_end");

     assert(_retained, "or else _true_end should be equal to _hard_end");

     assert(_retained_filler.end() <= _top, "INVARIANT");

     CollectedHeap::fill_with_object(_retained_filler);

     if (_top < _hard_end) {

       fill_region_with_block(MemRegion(_top, _hard_end), true);

     }

     HeapWord* next_hard_end = MIN2(_true_end, _hard_end + ChunkSizeInWords);

     _retained_filler = MemRegion(_hard_end, FillerHeaderSize);

     _bt.alloc_block(_retained_filler.start(), _retained_filler.word_size());

     _top      = _retained_filler.end();

     _hard_end = next_hard_end;

     _end      = _hard_end - AlignmentReserve;

     res       = ParGCAllocBuffer::allocate(word_sz);

     if (res != NULL) {

       _bt.alloc_block(res, word_sz);

     }

   }

   return res;

 }

 void

 ParGCAllocBufferWithBOT::undo_allocation(HeapWord* obj, size_t word_sz) {

   ParGCAllocBuffer::undo_allocation(obj, word_sz);

   // This may back us up beyond the previous threshold, so reset.

   _bt.set_region(MemRegion(_top, _hard_end));

   _bt.initialize_threshold();

 }

 void ParGCAllocBufferWithBOT::retire(bool end_of_gc, bool retain) {

   assert(!retain || end_of_gc, "Can only retain at GC end.");

   if (_retained) {

     // We're about to make the retained_filler into a block.

     _bt.BlockOffsetArray::alloc_block(_retained_filler.start(),

                                       _retained_filler.end());

   }

   // Reset _hard_end to _true_end (and update _end)

   if (retain && _hard_end != NULL) {

     assert(_hard_end <= _true_end, "Invariant.");

     _hard_end = _true_end;

     _end      = MAX2(_top, _hard_end - AlignmentReserve);

     assert(_end <= _hard_end, "Invariant.");

   }

   _true_end = _hard_end;

   HeapWord* pre_top = _top;

   ParGCAllocBuffer::retire(end_of_gc, retain);

   // Now any old _retained_filler is cut back to size, the free part is

   // filled with a filler object, and top is past the header of that

   // object.

   if (retain && _top < _end) {

     assert(end_of_gc && retain, "Or else retain should be false.");

     // If the lab does not start on a card boundary, we don't want to

     // allocate onto that card, since that might lead to concurrent

     // allocation and card scanning, which we don't support.  So we fill

     // the first card with a garbage object.

     size_t first_card_index = _bsa->index_for(pre_top);

     HeapWord* first_card_start = _bsa->address_for_index(first_card_index);

     if (first_card_start < pre_top) {

       HeapWord* second_card_start =

         _bsa->inc_by_region_size(first_card_start);

       // Ensure enough room to fill with the smallest block

       second_card_start = MAX2(second_card_start, pre_top + AlignmentReserve);

       // If the end is already in the first card, don't go beyond it!

       // Or if the remainder is too small for a filler object, gobble it up.

       if (_hard_end < second_card_start ||

           pointer_delta(_hard_end, second_card_start) < AlignmentReserve) {

         second_card_start = _hard_end;

       }

       if (pre_top < second_card_start) {

         MemRegion first_card_suffix(pre_top, second_card_start);

         fill_region_with_block(first_card_suffix, true);

       }

       pre_top = second_card_start;

       _top = pre_top;

       _end = MAX2(_top, _hard_end - AlignmentReserve);

     }

     // If the lab does not end on a card boundary, we don't want to

     // allocate onto that card, since that might lead to concurrent

     // allocation and card scanning, which we don't support.  So we fill

     // the last card with a garbage object.

     size_t last_card_index = _bsa->index_for(_hard_end);

     HeapWord* last_card_start = _bsa->address_for_index(last_card_index);

     if (last_card_start < _hard_end) {

       // Ensure enough room to fill with the smallest block

       last_card_start = MIN2(last_card_start, _hard_end - AlignmentReserve);

       // If the top is already in the last card, don't go back beyond it!

       // Or if the remainder is too small for a filler object, gobble it up.

       if (_top > last_card_start ||

           pointer_delta(last_card_start, _top) < AlignmentReserve) {

         last_card_start = _top;

       }

       if (last_card_start < _hard_end) {

         MemRegion last_card_prefix(last_card_start, _hard_end);

         fill_region_with_block(last_card_prefix, false);

       }

       _hard_end = last_card_start;

       _end      = MAX2(_top, _hard_end - AlignmentReserve);

       _true_end = _hard_end;

       assert(_end <= _hard_end, "Invariant.");

     }

     // At this point:

     //   1) we had a filler object from the original top to hard_end.

     //   2) We've filled in any partial cards at the front and back.

     if (pre_top < _hard_end) {

       // Now we can reset the _bt to do allocation in the given area.

       MemRegion new_filler(pre_top, _hard_end);

       fill_region_with_block(new_filler, false);

       _top = pre_top + ParGCAllocBuffer::FillerHeaderSize;

       // If there's no space left, don't retain.

       if (_top >= _end) {

         _retained = false;

         invalidate();

         return;

       }

       _retained_filler = MemRegion(pre_top, _top);

       _bt.set_region(MemRegion(_top, _hard_end));

       _bt.initialize_threshold();

       assert(_bt.threshold() > _top, "initialize_threshold failed!");

       // There may be other reasons for queries into the middle of the

       // filler object.  When such queries are done in parallel with

       // allocation, bad things can happen, if the query involves object

       // iteration.  So we ensure that such queries do not involve object

       // iteration, by putting another filler object on the boundaries of

       // such queries.  One such is the object spanning a parallel card

       // chunk boundary.

       // "chunk_boundary" is the address of the first chunk boundary less

       // than "hard_end".

       HeapWord* chunk_boundary =

         (HeapWord*)align_size_down(intptr_t(_hard_end-1), ChunkSizeInBytes);

       assert(chunk_boundary < _hard_end, "Or else above did not work.");

       assert(pointer_delta(_true_end, chunk_boundary) >= AlignmentReserve,

              "Consequence of last card handling above.");

       if (_top <= chunk_boundary) {

         assert(_true_end == _hard_end, "Invariant.");

         while (_top <= chunk_boundary) {

           assert(pointer_delta(_hard_end, chunk_boundary) >= AlignmentReserve,

                  "Consequence of last card handling above.");

           _bt.BlockOffsetArray::alloc_block(chunk_boundary, _hard_end);

           CollectedHeap::fill_with_object(chunk_boundary, _hard_end);

           _hard_end = chunk_boundary;

           chunk_boundary -= ChunkSizeInWords;

         }

         _end = _hard_end - AlignmentReserve;

         assert(_top <= _end, "Invariant.");

         // Now reset the initial filler chunk so it doesn't overlap with

         // the one(s) inserted above.

         MemRegion new_filler(pre_top, _hard_end);

         fill_region_with_block(new_filler, false);

       }

     } else {

       _retained = false;

       invalidate();

     }

   } else {

     assert(!end_of_gc ||

            (!_retained && _true_end == _hard_end), "Checking.");

   }

   assert(_end <= _hard_end, "Invariant.");

   assert(_top < _end || _top == _hard_end, "Invariant");

 }